ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
The triplet state energies, ET(0–0), for the α-oligothiophenes (αn's) with n=1–7, were determined and vary from 18 000 cm−1 (α2) to 13 000 cm−1 (α7). The data were obtained from spectroscopic and calorimetric measurements. It was found that the triplet energies decrease with the increase ring number (n), leveling off beginning with the α-oligothiophene with n=5. A linear relation was obtained for the triplet energy as a function of the reciprocal of n. The data has allowed the extrapolation to polythiophene (n=∞) and the evaluation of its triplet energy (≅10 000 cm−1). The energies (0–0) of the first singlet excited state of n=1–7 were also evaluated and again a linear relation was found for the E[S1(0–0)] as a function of 1/n. The S1−T1 energy splitting, ΔE(S1−T1), was determined and also found to decrease with the increase in the number ring. Semiempirical molecular orbital theoretical calculations reproduce this same trend of decreasing ΔE(S1−T1) with n. Extended FEMO theory was applied to the singlet and triplet energies as a function of the number of π electrons of the system. The data obtained are discussed regarding the length of the chain needed for an effective conjugation similar to that of the polymer (n=∞) and the geometries of the singlet and triplet states of the α-oligothiophenes. © 1999 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.479825
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